Copmpression unit for high and low pressure services

ABSTRACT

A compression unit for supplying high and low pressure services to a plant including a single driver associated with two driver shaft-ends projecting apart from the driver, a first driver shaft end and a second driver shaft end, a first unit being operatively connected to the first driver shaft-end and a second unit being operatively connected to the second driver shaft-end.

BACKGROUND

Embodiments of the present invention relate to a compression unit forsupplying a complete pressure service to a plant, the single compressionunit being capable of supplying high and low pressure services.

Within a process plant, to supply high pressure gas and low pressure gasseveral different units are usually provided to process different flowrates at different pressure values.

A main drawback of the prior art is the complexity of the overallarchitecture and configuration of the compression units, this leading tobulky apparatus.

In fact, usually separate units are used to provide gas at differentpressure values to a process plant, each of such compression unitscomprising a dedicated driver and associated impellers which increasethe overall dimensions of the units.

SUMMARY

An embodiment of the present invention relates to a single compressionunit for supplying a complete compression service consisting of high andlow pressure gas to a process plant.

The compression unit is configured to supply high and low pressure gasflow with a simple architecture and with a configuration which reducesoverall dimensions and weight of the unit, and also has an increasedefficiency with respect to the state of the art.

In order to better clarify what is to be intended with the terms “high”and “low” pressure reference to the compressor flanges rating, accordingto ANSI, will be done hereafter.

As known in the art, technical limits exist while designing an impeller.One of these limits is represented by the peripheral speed of theimpeller.

It is known in the art that impellers having a large diameter canprocess a high flow rate but work with reduced rotational speed and,therefore, a limited compression ratio. In order to give typical values,the term “low” pressure here indicates rating values within a typicalrange comprised between 150 and 300, while the impeller can process aflow rate which could be comprised in a range between 50.000 and 200.000m3 per hour.

A typical speed value of an impeller processing said flow rates is 5.000to 1.800 rounds per minute thus indicated for a direct coupled solution.

The term “high” pressure here indicates typical rating values comprisedbetween 300 and 2500, with an inlet pressure value between 3 and 50 barfor the first impeller. In order to reach very high compression rates,the impeller processes low flow rates, typically less than 50.000 m3 perhour.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and specific embodiments will refer to the attacheddrawing, in which:

FIG. 1 is a schematic representation of one embodiment of thecompression unit;

FIG. 2 is a schematic representation of the compression unit accordingto an embodiment.

DETAILED DESCRIPTION

The following description of exemplary embodiments refers to theaccompanying drawings. The following detailed description does not limitthe invention. Instead, the scope of the invention is defined by theappended claims.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with an embodiment is included inat least one embodiment of the subject matter disclosed. Thus, theappearance of the phrases “in one embodiment” or “in an embodiment” invarious places throughout the specification is not necessarily referringto the same embodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Such compression unit 1 comprises a single driver 2 associated with twodriver shaft-ends, and in one embodiment projecting apart from saiddriver 2 along opposite directions, a first driver shaft end 3 and asecond driver shaft end 4.

In order to better describe the compression unit according toembodiments of the present invention, it can be considered that thedriver 2 divides the compression unit into two sides; on one side, afirst unit 10 is operatively connected to the first driver shaft-end 3,while a second unit 20 is operatively connected to the second drivershaft-end 4.

According to an embodiment of the present invention, said first unit 10comprises an impeller 11, and said second unit comprises a bull gear 21in an integrally geared-compressor arrangement.

More particularly, according to an embodiment said impeller 11 of saidfirst unit 10 is an overhung impeller directly connected to the firstdriver shaft-end 3, and in one embodiment by means of a flangedconnection or a flexible coupling.

According to an embodiment of the present invention, an overhungimpeller is an impeller having no bearing/s on the opposite side withrespect to the driver, thus all bearing/s of the overhang impeller arearranged between the impeller and the driver.

In this case, the impeller 11 of the first unit is the “low” pressuresource unit: typical values of flow rate processed by the overhungimpeller are about 50.000 m3 per hour, with an inlet pressure value ofaround 1 bar and an outlet pressure value of about 2 or 3 bar.

On the other side, the bull gear 21 is in one embodiment connected bymeans of a flanged connection, or a flexible coupling, to said seconddriver shaft-end 4.

According to an embodiment shown in FIG. 1, said second unit 20comprises the bull gear 21 which drives at least one driven shaft 22, 23through pinions in a typical integrally geared-compressor arrangement.In order to obtain higher outlet pressure values, the bull gear 21comprises two or more driven shafts, for example a first driven shaft 22and a second driven shaft 23, which are drivingly connected to the bullgear 21 by means of respectively pinions.

Said pinions are teethed wheels having a diameter smaller than thediameter of the bull gear. The pinions are engaged directly on the bullgear so that the rotation of the latter produces the rotation ofpinions.

Each of said driven shafts supports at its opposite ends an overhungimpeller 22 a, 22 b, 23 a, 23 b.

According to an embodiment of the present invention, the two drivenshafts 22, 23 are configured to rotate at different rotary speed.

Typical flow rate values for the second unit 20 are about 50.000 and200.000 m3 per hour, with casing rating varying between ANSI 300 and1500.

According to the first embodiment of the compression unit 1 shown inFIG. 1, the driver 2 drives the single overhung impeller 11 connected tosaid first driver shaft 3.

On the other side of the compression unit 1, the same driver 2 drivesthe bull gear 21 which comprises in one embodiment two driven shafts 22,23, the first driven shaft 22 supports at its ends a couple of firstoverhung impellers 22 a, 22 b, the second driven shaft 23 supports atits ends a couple of second overhung impellers 23 a, 23 b.

According to the scheme of FIG. 1, the first overhung impellers 22 a, 22b and the second overhung impellers 23 a, 23 b are fluidly connected sothat the gas flow passes through the first overhung impellers 22 a, 22 bof the first driven shaft 22 and then through the second overhungimpellers of the second driven shaft 23, thus forming a first multistage compression unit for compressing a small flow rate up to highpressure values. This configuration is illustrated in FIG. 1 by means ofdashed lines indicated with the reference number 40 which represent thehydraulic connection between the impellers.

According to an embodiment of the present invention, the outlet of theoverhung impeller 11 of the first unit 10 is fluidly connected to theinlet of the second unit 20, thus forming a second multi stagecompression unit. This configuration is represented in FIG. 1 by meansof dashed line 30 which represent the hydraulic connection between theunits.

In this configuration, the first unit 10 provides the gas flow rate tothe second unit 20 thus obtaining a compression unit apt to elaboratelarge flow rates with an high overall compression rate.

According to an embodiment of the present invention not shown in thedrawings, the first unit 10 comprises an overhung impeller 11 which isconnected to said first driver shaft 3 by means of a gear arrangement,instead that flanged to said first driver shaft.

According to an embodiment of the present invention shown in FIG. 2, thefirst unit 10 comprises a beam compressor. Said beam compressor may beflanged to said first driver shaft 3 or, alternatively, the beamcompressor may be connected to said first driver shaft 3 by means of agear arrangement.

Typical beam compressor casing rating varies from ANSI 600 to API 15000.

When the first unit 10 comprises a beam compressor, the inlet of thebeam compressor may be hydraulically connected to the output of the bullgear 21 of the second unit 20. According to this arrangement, the firstunit 10 receives the flow rate coming from the output of the second unit20, thus forming a third multi stage compression unit allowing to reachhigher compression rates. The hydraulic connection between the first 10and the second 20 unit is represented in FIG. 2 by means of the dashedline 50.

The compression unit according to an embodiment of the present inventiontherefore solves the drawbacks afflicting the prior art.

One of the results achieved with the compression unit according to thepresent invention is to reduce the footprint of the apparatus, with anextremely versatile configuration.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.

What is claimed is:
 1. A compression unit for supplying high and lowpressure services to a plant, the compression unit comprising: a singledriver associated with two driver shaft-ends projecting apart from thedriver; a first driver shaft end and a second driver shaft end; and afirst unit being directly operatively connected to the first drivershaft-end and a second unit being operatively connected to the seconddriver shaft-end, wherein the first unit is an overhung impeller, andthe second unit is an integrally geared-compressor arrangementcomprising a bull gear and a plurality of pinions engaged with the bullgear, wherein the diameter of bull gear is larger than the diameter ofpinions.
 2. The compression unit according to claim 1, wherein theoverhung impeller of the first unit is an impeller connected to thefirst driver shaft-end by a gear arrangement.
 3. The compression unitaccording to claim 1, wherein the bull gear is connected by a flangedconnection to the second driver shaft-end.
 4. The compression unitaccording to claim 1, wherein the integrally geared-compressorarrangement comprises at least one driven shaft.
 5. The compression unitaccording to claim 4, wherein at the opposite ends of the at least onedriven shaft are provided overhung impellers.
 6. The compression unitaccording to claim 4, wherein the bull gear comprises two driven shafts,a first driven shaft and a second driven shaft, each of the first andsecond driven shaft being provided at its ends with a couple of overhungimpellers, respectively first overhung impellers and second overhungimpellers.
 7. The compression unit according to claim 1, wherein thefirst overhung impellers and the second overhung impellers are fluidlyconnected thus forming a first multi stage compression unit.
 8. Thecompression unit according to claim 1, wherein an outlet of the firstunit is fluidly connected to an inlet of the second unit, forming asecond multi stage compression unit.
 9. The compression unit accordingto claim 1, wherein the inlet of the first unit is fluidly connected tothe outlet of the second unit, forming a third multi stage compressionunit.
 10. The compression unit according to claim 1, wherein the drivershaft-ends are the ends of a single driver shaft.
 11. The compressionunit according to claim 1, wherein the two driven shafts are configuredto rotate at different rotary speeds.